Many drugs are mixed with a diluent before being delivered to a patient because the mixture tends to be unstable. The diluent may be, for example, a dextrose solution, a saline solution or water. Many such drugs are supplied in powder form. Thiopental sodium and water solutions for injection need to be mixed in a sterile manner promptly before use with unused portions discarded within 24 hours.
Liquid from a first container may be mixed with a powder compound in a second container by inserting a needle-like hollow conduit which is coupled to the first container through a sealing diaphragm of the second container. Examples of this type of apparatus are illustrated and described in U.S. Pat. Nos. 4,392,850 and 4,392,851, 3,882,909, and 4,336,802. One problem with this approach is that mistakes can be made and the wrong liquid and powder can be combined. Another problem is that there can be a mishap and sterile conditions can be lost. Still another problem is that the process is somewhat complicated. Furthermore, the wrong proportions of liquid and/or powder can be combined.
U.S. Pat. No. 4,331,233 illustrates and describes a two-compartment vial with a plug sealingly seated in a constricted portion which selectively separates and isolates powder stored in a lower chamber from liquid stored in an upper chamber. A flexible stopper fits in an opening at the top of the vial and extends into the vial. Pushing down on the stopper causes a force to be exerted on the liquid which in turn exerts a force on the plug that dislodges the plug and causes it to be displaced into the lower chamber. This allows liquid in the upper chamber to flow into the lower chamber and mix with the powder. One problem with this vial is that it is difficult to get the powder into the lower chamber without getting some of it on the walls of the upper chamber. When the liquid is poured into the upper chamber it activates with the powder on the side walls of the upper chamber. This premature mixture of improper proportions, which can degrade with time, can destroy the purity of the mixture subsequently formed. One solution to this problem could be to clean the upper chamber after the lower chamber is filled and the plug is inserted. This adds to the cost and complexity of manufacture. Another problem of manufacture is that it is not easy to insert the plug into a sealing position since nothing is connected to the plug. Another problem is that if the amount of liquid does not completely fill up the upper chamber then there is an air pocket which must be compressed before the force applied to the top stopper is transmitted to the liquid and then to the plug. The changing of the locations of the powder and liquid leads to a potentially more difficult operation since some powders compress under pressure and accordingly, more force must be applied to dislodge the plug.
A drug known as topicycline (tetracycline hydrochloride for topical solution) is produced for Proctor & Gamble and is sold in mixing and dispersing apparatus. The apparatus, which includes a glass bottle containing liquid and having a threaded top portion that defines an opening therein, a stopper, a screw-on cap, and an applicator which contains powder medication, allows the liquid and the powder to be mixed in the bottle. As taken from the provided package, the bottle is partly filled with a liquid which is 40% ethanol, citric acid and n-decyl methyl sulfoxide. It has a stopper inserted into the opening at the top and has the cap screwed onto the top of the bottle. The cap is first removed and then the stopper is removed and discarded. The applicator, which is packaged in what appears to be a sealed sterile wrapping, is removed from the wrapping and inserted into the top of the bottle. Within a chamber of the applicator there is contained a powder which is tetracycline hydrochloride, 4-epitetracycline hydrochloride, and sodium bisulfite. The applicator is cylindrical, has a semi-spherical flexible top member, a piston member, and an ejectable cylindrical bottom sealing member. The piston member engages the top and bottom members of the applicator and is displaced when the top member is pressed such that the sealing bottom member is discharged from the applicator and falls into the liquid in the bottle. The powder in the chamber then falls into and mixes with the liquid. The top member has a series of apertures therethrough which permits the mixture to be applied to the skin after the cap is removed. One problem with this apparatus is that the mixing operation is not sterile since the bottle is open to the air and the applicator must be handled and therefore can be contaminated by air borne contaminants or by contaminants on the hands of a preparer of the mixture. It is also possible that if different applicators and bottles are stored together that the wrong applicator and bottle might be combined.
It is desirable to have apparatus in which a powder and a liquid can be mixed in such a manner that sterile conditions are maintained, the proportions of the two ingredients being mixed are always correct, nothing can leak out, and the process is simple, easy to perform, and essentially fool proof.